Electronic devices generate heat during operation. Thermal management refers to the ability to keep temperature-sensitive elements in an electronic device within a prescribed operating temperature. Thermal management has evolved to address the increased heat generation created within such electronic devices as a result of increased processing speed and power within the electronic devices.
Electronic devices were historically cooled by a natural convection thermal management technique. The cases or packaging of these prior art electronic devices were designed with openings (e.g., slots) strategically located to allow warm air to escape and cooler air to be drawn in.
The advent of high performance processors and electronic devices now requires more innovative thermal management. Each increase in processing speed and power generally carries a cost of increased heat generation such that natural convection alone is no longer sufficient to provide proper thermal management.
One common method for cooling electronic devices, such as an integrated circuit that includes a high performance processor, is by thermally coupling a heat sink to the processor. As used herein, processor means any type of computational circuit such as, but not limited to, a microprocessor, a microcontroller, a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a graphics processor, a digital signal processor (DSP), or any other type of processor or processing circuit. Processors typically require more innovative thermal management when compared to other types of integrated circuits because of their large size, high speed and high component count.
A heat sink is a thermal dissipation device comprised of a mass of material that is thermally coupled to a heat source to conduct thermal energy away from the heat source. The heat sink conducts the thermal energy away from a high-temperature region (i.e., the processor) to a low-temperature region (i.e., the heat sink). The thermal energy is then dissipated by convection and radiation from a surface of the heat sink into the atmosphere surrounding the heat sink.
A well-known technique for improving the efficiency of a conductive heat sink is to provide a greater surface area on the heat sink. The increased surface area is typically provided by a number of fins that are attached to a base portion of the heat sink. The fins allow the heat sink to dissipate a greater amount of thermal energy from the heat sink into the atmosphere.
The base of the heat sink device may have many different forms. The base typically includes one or more surfaces that are thermally coupled, directly or indirectly, to an integrated circuit that includes a processor in order to dissipate heat from the processor. Thermal energy is conducted from the processor through the heat sink base into the fins. The heat is dissipated into the atmosphere by convection through the top surface of the base and the surface of fins.
The fins are either integral with the base of the heat sink or assembled to the base using various conventional fastening techniques. In heat sinks where the base and the fins are assembled together, the base is typically either copper or aluminum, and the fins are either copper or aluminum. Copper has superior thermal conductivity as compared to aluminum, but is significantly more expensive. Copper is also much denser, adding significant weight to the heat sink and making the heat sink, and the electronic device where the heat sink is located, more vulnerable to damage from shock and/or vibration. Therefore, heat sinks that have copper are heavy and costly while aluminum fins do not provide enough thermal performance.
An alternative and more costly system to manage the thermal energy output of high-powered processors utilizes heat sinks in combination with a fan. The fan forces air or some other fluid over and around a surface of the heat sink and/or processor in order to dissipate a greater amount of thermal energy from the processor.
There are several problems with cooling systems that include a heat sink and fan combination. One problem is that the fan must typically be located too closely to the fins of the heat sink to generate fully developed air flow. When a large fan is used in conjunction with a heat sink to cool an electronic component, a large percentage of the air moved by the system fan does not go through the heat sink. As a result, even large fans are not an efficient solution for cooling some electronic devices.
Some cooling systems utilize multiple fans to maintain proper operating temperatures. However, the additional fans add unwanted expense to manufacturing such electronic devices. In addition, extra fans are noisy, bulky, and utilize an inordinate amount of space within the environment where the electronic device is located.
Since existing heat sinks do not cost-effectively cool high performance processors, what is needed is a cost-effective heat sink that provides high performance cooling for electronic components with high power generation.